Manufacture of sulphur derivatives of organic compounds



Patente d May 16,1944

MANUFACTURE or SULPHUR DERIVATIVES or oacsmc CQMPOUNDS John F. Olin andThomas E. Deger, Grouse Ile, Mich, assignors to Sharples Chemicals Inc.,a-

corporation of Delaware No Drawing. Application January 21, 1941,

S arial No. 375,366

4 Claims. (Cl. 260-608) The present invention pertains to themanufacture oi chemical compounds consisting of two organic radicalslinked by a sulphur chain consisting of two or more sulphur atoms. Whilethe invention may bepracticed in the manufac- -ture of compounds of thistype. in which the organic radicals are alkyl, and, aralkyl, cycloalkyl,orheterocyclic, it was conceived as the result of research to develop aneconomical method of producing dibenzyl disulphide. It will accordinglybe discussed with reference to that problem, with the understanding thatit may be applied in the manufacture of polysulphide derivatives ofother 'aralkanes or of. the various other organic compounds discussedabove.

In the manufacture of dibenzyl disulphide by prior art methods, it hasbeen customary to react benzyl chloride with an alkali metal compound ofthe type or disodium disulphide, in accordance with the followingequation:

Various procedures have been proposed for applying this reaction. Thus,some of these proposals have been as follows:

(a) That the reaction be conducted in an ethyl alcohol solution.

(b) v'lhat the reaction be accomplished in an aqueous medium, followedby performance of special purification steps on the resulting reactionmixture.

(c) That the reaction be conducted in a heterogeneous mixture obtainedby dissolving the di-= sodium disulphide in water and dissolving thebenzyl chloride in an organic solvent suchas alinto benzyl mercaptan bysulphydrolysis andathen' converts the mercaptan to dibenzyl disulphideby oxidation of the 'mercaptan, as will be evident from the followingequations, in which X represents an oxidizing agent:'

Basic catalyst 4. 2C H CHiSH S CuHICHi SHQCHSCt a A particular featureof the practice of the invention in its preferred form consists in thefact that the benzyl chloride is first reacted with an alkali metalhydrosulphide in a reaction mixture containing a molecular excess of thehydrosuh phide (Equation 2 above),' and that sulphur is then added tothe reaction mixture to effect oxidation thereof without first removingthe excess alkali metal hydrosulphide. By operating in this manner; adual advantage is obtained. In the first place, by using a molecularexcess f the hydrosuiphide in Equation 2, the react on is caused toproceed rapidly to the right. This advantage might under ordinarycircumstances be somewhat counterbalanced by added difficulty due to thenecessity of added purification expense in removal of excess alkalimetal hydrosulphide. but by using the excess hydrosulphide to catalyzethe ensuing oxidation reaction, we turn this apcohol, and then mixingthe two solutions to obtain the desired reaction.

These processes leave something to be desired .from the standpoint ofboth economy and purity of product, and the object of the presentinven-; tion has been to provide a process which constitutes animprovement over the prior-art in these particulars. Prior art processeshave provided v a reaction product which contains a substantialproportion of impurities, with the result that it has an objectionablered or pink color. A featureof the present invention consists in thefact that the product is free of the impurities which result in this redor pink coloration, the product obtained by the process of thisinvention being practically colorless. I

- In the practice oi the invention, instead of sulparent disadvantageinto an actual advantage.

It is not necessary to maintain a large amount of alkali metalhydrosulphide in the reaction mixture when the benzyl mercaptanisioxldized in accordance with Equation 4, since the function of thisconstituent is catalytic, and it accordingly performs this function eventhough it may be resent in an amount which is far short or astoichiometric equivalent of the constituents to be reacted.

In the detailed performance 0! the invention, the benzyl chloride, whichmay be employed in the purified'form or in the form of .a crude reactionmixture consisting of benzyl chloride and toluene as obtained in thechlorination of toluene, may be slowly added to an aqueous sodiumhydrosulphide solution,.while heating the solution to a temperaturebetween and C. and

' stirring the mixture. The stirring and heating are preferablycontinued for a period between one and five hours, until the benzylchloride has been substantially completely converted into the mercaptan(Equation 2).

It the reaction mixture were allowed to settle. it would separate intotwo layers, an upper oil layer consisting essentially oi benzylmercaptan or a mixture of benzyl mercaptan with toluene,

and a lower aqueous layer consisting of a solution of salt and sodiumhydrosulphide. But instead of separating the aqueous solution at thispoint, it is retained in the mixture while sulphur is added insuiiicient quantity to oxidize (sulphurize) the benzyl mercaptan toproduce the desired dlbenzyl disulphide at a temperature oi. 70 to 95 C.with stirring. Stirring and heating are continued for a period betweenone and five hours in Order to complete the reaction of Equation 4.

Hydrogen sulphide evolved in accofliance with Equation 4 may be absorbedin a sodium sulphide or sodium hydroxide solution (see Clark Patent2,147,400) in order to regenerate sodium hydrosulphide for use insubsequent practice of the steps of Equation 2. 1

After the reaction between the sulphur and benzyl mercaptan has beensubstantially completed to convert the mercaptan into the correspondingdlbenzyl disulphide, the crude reaction product may be washed with waterto .remove most of the salt and then steam distilled in the presence ofa small amount of a base to completely remove traces of benzyl mercaptanand toluene. The residue of dlbenzyl disulphide and the base is washedseveral times with water to remove water soluble constituents of themixture. The wet dibenzyl disulphide may then be dried under vacuum atabout 80. C. and filtered to remove dirt and other insolubleconstituents. The final product is a fairly hard crystalline massmelting between 65 and 68 C. It gives a negative copper corrosion testresult even when treatedfor one hour at 200 F. I

The following specific examples afford iurthe illustrations of thepractice of the invention.

Example I 1120. lbs. of 38.7% aqueous sodium hydrobenzyl mercaptan asshown by the fact that the oil layer analyzes 90% benzyl mercaptan. Without removing the aqueous layer from the digester 100 lbs. sulphur areadded over a period of 3 hours at 85-90" C. This phase of the process isdone in a closed system so that the hydrogen sulphide that is formed canbe absorbed in a system of three gas scrubbers in series containingapproximately 27% sodium hydroxide solution. The hydrogen sulphide iscompletely absorbed and none escapes to contaminate the atmosphere. Thesodium hy drosulphide solution formed in the scrubbers may be used insubsequent batches for the production 01' the mercaptan. The slightmolar excess of sodium hydrosuliide adds :1 at the beginning serves as acatalyst during the oxidation 01' the benzyl mercaptan with sulphur.After all the sulphur is added the mixture is heated for 6 hours at90-95 C..with stirring. 120 lbs. sodium hydroxide priate shippingcontainers.

are added and the mixture is wet distilled at approximately 40 mm.pressure. This step serves to remove traces of unreacted benyl chlorideand benzyl mercaptan from the dibenzyl disulphide. About 100 gallons ofdistillate are collected containing approximately gallon oil layer. Theheavy water layer containing sodium chloride, sodium hydrosulphide,sodium hydroxide and traces of sodium benzyl mercaptide is removed fromthe dlbenzyl disulphide oil layer. The oil layer is then washed fourtimes with approximately 250 gallon portions of water while maintainingit in a molten state at -85 C. to remove soluble inorganic material. Thewater layers are separated after the benzyl disulphide has been cooledand crystallized in order to aid in more complete removal of the waterlayer. After the .last water wash, the wet dlbenzyl disulphide is driedby vacuum at and 30 mm. pressure. While still in the molten state it ispassed through a filter press to remove dirt and iron sulfide. Thefiltrate is allowed to cool and solidify in appro- The product thusobtained is an almost white or very light pink, hard, crystalline solidmeltingat 67.5 C. and non-corrosive to copper on contact up to 45minutes at 200 F. 766 pounds finished dlbenzyl disulfide are obtained ina 96% yield based on benzyl chloride added.

Example II 124 grams benzyl mercaptan and 1 gram triethylamine areplaced in a flask equipped with a mercury seal stirrer, thermometerwell, catalyst adder, and reflux condenser attached to a scrubbing towerin which 20% sodium hydroxide flows counter current to the stream ofgas. Alter heating to C., 16 grams sulphur are added over a period ofhour. The hydrogen sulphide passes through the reflux condenser and isabsorbed in the sodium hydroxide solution. The crude product is washedonce with 10% sodium hydroxide solution followed by three washes withwater at 80-80 C. Aiterdrying at 80 C. under 30 mm. pressure'the moltendlbenzyl disulphide is filtered to remove dirt and allowed to cool andcrystallize. A product consisting of 122 grams of pure dibenzyldisulphide, almost white in color and melting at 67 C. is obtained. Theyield based\on benz mercaptan is 99%.

Various modifications will be obvious to those skilled in the art. Forexample, while a feature of the invention consists in the use 01' theexcess alkali metal hydrosulphide employed in sulphydrolysis as thecatalyst for the ensuing oxidation and sulphurizatlon reaction, theinvention may be practiced by sulphurizing the benzyl mercaptan with theaid of other catalysts as exemplified by the procedure of Example II,above. While the invention has particular utility in l the manufactureof di-aralkyl disulphides (e. g.'.

dlbenzyl disulphide), because of the ease with which compounds of thistype enter into metathetical reactions (e. g., the sulphydrolysis ofbenzyl chloride), the principles of the invention may be applied insulphydrolysis of various organic chlorides and oxidation of theresulting mercaptans, as indicated in the introductory remarks of thisspecification.

We wish it to be understood that the invention is not to be limited bythe details of the procedure discussed above, as these details arepurely illustrative. and that the invention is to be limited only by thescope of the following claims.

' ing aralkyl halide with sulphide in the presence oi! a quantity ofsaid We claim:

1. In the manufacture oi polysulphide compounds of the type representedby the formula RSSR, wherein R represents an aralkyi radical, theprocess comprising reacting the correspondan alkali metal hydroalkalimetal hydrosulphide in excess of a stoichiometric equivalent of thequantity of aralkyl halide treated to produce a mercaptan and:thereafter oxidizing the mercaptan of the resulting reaction mixture inthe presence of sulphur and unreacted alkali metal hydrosulphide of saidreaction mixture to produce the desired polysuiphide.

2. In the manufacture of di-aralkyl polysulphides, the processcomprising reacting an aralkyl halide with an alkali metal hydrosulphidein the presence of a quantity of said alkali metal hydrosulphide inexcess of the quantity of aralkyl halide under treatment to produce amercaptan, and thereafter oxidizing the mercaptan oi the resultingreaction mixture in the presence of sulphur and unreacted alkali metalhydrosulphide oi the reaction mixture to produce th desiredpoiysulphide. 4

3. In the manufacture of dibenzyl disulphide, the process comprisingreacting a benzyl halide with an alkali metal hydrosulphide in thepresence of a stoichiometric excess ofsaid alkali metal hydrosulphide toproduce a mercaptan and thereafter oxidizing the mercaptan of theresulting reaction mixture in the presence of sulphur and unreactedalkali metal hydrosulphide bi the reaction mixture to produce thedesired polysulphide.

4. In the manufacture of dibenzyl disulphide, the process comprisingreacting an alkali metal hydrosulphide with a benzyl halide in admixturewith toluene in the presence of a stoichiometric excess of said alkalimetal hydrosulphide to produce a benzyl mercaptan and thereafteroxidizing the benzyl mercaptan of the resulting reaction mixture in thepresence of sulphur and unreacted alkali metal hydrosulphide of saidreaction mixture to produce the desired dibenzyl disulphide, and finallyremoving toluene from the dibenzyl disulphide formed by the oxidationreaction.

JOHN F. OLIN. THOMAS E. DEGER.

CERTIFICATE OF CORRECTION.

Patent No. 2,514.9,191. 'May 16, 19%.

JOHN F; OLIN, ET AL;

It is hereby certified that error appears in'the printed specificationof the above number-ed patent requiringhorrection as follows: Page 2,sec- 0nd column, line M4, for '80-80 C. read --7080 C. and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case ih the Patent Office.

Signed and sealed this hth day of July, A. D. 19hh..

Leslie Frazer (Seal) Acting Commissioner of Patents.

